Regarding the stand-alone table, I'd suggest just google-ing List of US States and you should be able to find something you can copy/import into Quickbase.
Next, the relationship. Once you have your States table created, set the State Name as the key field. Next, create a relationship to the Customers table where the State is the Parent. Then, change the new 'Related State' field to a Formula Text field where the formula is just the [Address: State/Region] field. Finally, in the relationship, bring over your 'Nexus' field as a Lookup.
------------------------------
Blake Harrison
bharrison@datablender.io
DataBlender - Quickbase Solution Provider
Atlanta GA
404.800.1702 /
http://datablender.io/------------------------------